OK - a bit of free thought here, open to any input/opinions. I figured I'd post the debate going on in my head just to see what others might consider doing.

I have my A550, which has been excellent - I have pretty much all the lenses I need currently. My primary photography tends to be birding/wildlife, travel and architecture, low light/high ISO, night shooting, then scenic and landscape, in about that order. I use viewfinder for most of my shooting, but consider live view to be an absolute must for some off-angle shooting and for night tripod work - the A550 solution has been brilliant. My camera is still fine, but just getting on - over 2 years old, over 80K clicks...it's usually around the time I start considering a new body. I'm a JPG shooter most of the time, by choice - I hate post processing and don't like spending time in front of computers, so I like to get as many of my settings right in-camera, and working on exposure/metering while shooting...so JPG engines are very important.

When the A580 came out, it was immediately tempting as a replacement for my A550 - slightly better sensor, slightly better high ISO, adds multistack ISO, adds more focus points and two more cross-point sensors, increases battery life, adds a few more controls, otherwise looks, acts, and feels very much like my A550 (a positive for me).

Now with the A77, I'm torn. Things I love: many more cross-point focus sensors, more focus points, faster focus system, tracking focus likely better, faster burst, quieter, weatherproofed, more controls, more customization, memory banks for stored settings, large body, thick grip, huge resolution at low ISO, minimum ISO 50, better LCD articulation and flexibility. Things I would be worried about compared to A580: battery life much poorer, high ISO not as good, EVF an unknown quotient for me as I've not liked past versions, smaller buffer (or more quickly overwhelmed due to file size), more expensive.

Being that high ISO is very important to me when shooting, I worry that going to the A77 will leave me feeling like a downgrade from the A550, and far from the A580's potential. And I'm worried despite improvements with the EVF that I'm still going to experience eye-strain and lag effects tracking birds. And the battery life is really something that digs on me - I am accustomed to charging my A550 once, and firing off 3,500+ shots over 2-3 days without any worries. Yet I can see some clear advantages to the weatherproofed, superfast body with electronic first curtain shutter and lots of cross AF sensors.

I also have my NEX3 - and have considered upgrading it to the NEX-5N. It's my second body, for lightweight duties and occasional substitute duties. I'm wondering if maybe I could manage to separate in my mind my high ISO shooting needs for low light from my other shooting - maybe getting the A77 to shoot daylight, long exposure, and wildlife/birding, with ISO looking fine to ISO1600...and get used to using the NEX-5N for high ISO handheld work. Downsides to that theory are that the NEX has no fast autofocus lenses, whereas I have my 30mm F1.4 and 50mm F1.7 on my DSLR for those needs...and the NEX has no in-body stabilization, so even using manual fast lenses, I can gain several stops with the DSLR due to the SSS system. Not to mention, the extra cost of upgrading to the A77 and the NEX-5N...it would be much cheaper to grab the A580 and NEX-5N, or even hold onto my NEX-3 for a little longer, since the A580 can do excellent high ISO work.

The A550 JPG engine has been quite good - the A580 seems even better, so no worries there. The noise performance of the 16MP sensor is excellent - not only better at higher ISOs with lower noise, but less intrusive noise, since it's mostly lumi. The biggest issue I have with the A77 is that the noise seems much higher in chroma - and much of that very destructive to fine patterns and detail when removed...leaving blotchy patches. The 14MP and 16MP sensors are virtually free of chroma, no blotchiness, and with a nice, fine grained luminance noise pattern. Even considering the resolution advantage of 24MP which could be downsized to 16MP and compared, I still see much uglier blotchiness and NR smearing at ISO3200 and up, and I shoot there often.

So, there are all the things swimming around in my head. It doesn't help that some of these temptations are hitting me now, with a bit over 2 weeks to go before I'm on a 2-week vacation in Canada and New England - even though I have absolutely no need for any new camera, part of me wants to get one or both before I go.

Tough call, the a580 is priced so well you should almost buy it just out of boredom if for no other reason.
I think the tracking and focus lock on the A77 may be worth it just by itself, especially when panning a bird in flight. There is always the less expensive A65 to consider as well.

My advice, if your not sure what to do ... do nothing.
* photo courtesy of Gustav

I think Westcoast is onto something, if not sure wait. Still the A77 sounds pretty good, weathersealing is pretty valuable for me anyway, maybe wait for the price to drop more. Had the A77 come out a year ago chances are I might not have strayed to Canon.

Its the unreliability issues in variable weather conditions that annoyed me the most with my Sony A100. It had been back under warranty and had components replaced, but it didn`t fix the unreliability issues under warm to hot weather and humid conditions.

Good points - the A580 price is certainly fantastic - considering it's cheaper than I got the A550 for over 2 years ago! I find the A77 price perfectly palatable too - if I could get over my high ISO worries, I could accept the extra battery need and could probably work with the EVF considering most have noted it's far better than the A55 unit...and I absolutely love the tracking, focus, and speed specs.

I'm hoping some more shots can be posted showing A77 shots resampled down to 16MP to see how they match up to the A580 - though the high ISO performance is clearly not as good, it's also not BAD - and the extra res might be enough that the resized shots can close the gap quite a bit with the 16MP sensor's performance. I think the A580 will still ultimately be a little cleaner at the highest ISOs...but if I could get ISO3200 to look clean, it could work.

There are so many things I love about the A77's body and controls, and speed. Very tempting. And there are so many things I love about my A550 that are improved on the A580. There were the questions on whether or not the A580 was enough of an upgrade from the A550, and whether there were too many questionmarks and worries with the A77/A65.

In the end, two primary things made my decision: 1. High ISO, 2. Battery. With a backup push coming from my still slight hesitation to go with EVF which though massively improved is still worrysome. So I'm going with WestCoast's advice...I bought the A580.

What I have not liked about the A77 high ISO performance isn't that I find it necessarily all that much more noisy than the A580 - with the resized shots and proper RAW processing they'd probably be a near match. But I don't want to have to RAW process and downsize my shots - I prefer good out-of-camera JPGs, and the JPG engine in the A77 still looks like it needs a good firmware fix - just to blotchy, too swirly in the removal areas, lines of contrast still too hazy and bleedy...the A580 JPGs at the higher ISOs simply look better, across the board. Moreover, they look better than those from my A550 - it's not huge, but noticeable, especially at ISO6400 and 12800. With the addition of multistack ISO, the difference becomes massive.

With the increased battery life, the increased focus points, the increased ISO performance, the additional controls and features (CDAF main sensor live view, DOF preview with lens button mapping), the addition of ISO100, and the multistack ISO addition, I'm confident it will be a lovely upgrade to my A550 - everything I like and am familiar with, plus significant improvements across the board, and no worries about high ISO, EVFs, and battery life.

That said, the A65/A77 is right on the cusp for me, and very very tempting still. With very small changes, I can see this easily becoming an overwhelmingly tempting camera and being next in line to replace the A580. I already know it will be superior to focus and track, which I could use, and in shooting speed. If they can work on increasing battery life to something in the 800-900 CIPA range, and can clean up the JPG engine for high ISO...even the crazy idea of making a 16MP version (which I think in all honesty I would have bought without hesitation)...I could get past the EVF doubts and the SLT worries.

For now, I'll go with what may be the last Sony OVF camera, and push one more generation to see what the A65/77 morphs into in second gen, or even with some significant firmware updates. If photo sales go well, who knows - I might even decide to add one alongside the A580 mid-year next year.